Photoflash array with selective pairing of lamps

ABSTRACT

A photoflash lamp array having a plurality of 2n flashlamps, a common terminal connected to one lead-in wire of each of the lamps, and a plurality of n selective terminal means, each associated with a respective pair of the lamps and directly connected to the non-common lead-in wire of one lamp of each pair. A respective normally open switch is coupled between the non-common lead-in wires of each of the pairs of lamps associated with a selective terminal. Each of the switches is responsive to the flashing of the directly connected lamp of an associated pair so as to electrically connect the other lamp of the pair to the associated selective terminal. In one specific example, ten lamps are selectively paired to be operated sequentially by firing pulses successively applied to five selective terminals together with a common terminal.

BACKGROUND OF THE INVENTION

This invention relates to photoflash lamp arrays having circuit meansfor causing a different lamp to be flashed upon each occurrence of afiring pulse produced in synchronism with the opening of a camerashutter.

Numerous multilamp photoflash arrangements with various types ofsequencing circuits have been described in the prior art. Series andparallel-connected lamp arrays have been shown which are sequentiallyfired by mechanical switching means, simple electrical circuits,switching circuits using the randomly varied resistance characteristicsof the lamps, arc gap arrangements, complex digital electronic switchingcircuits, light-sensitive switching means and heat-sensitive switchingdevices which involve melting, fusing or chemical reaction in responseto the radiant energy output of an adjacently located flashlamp.

One currently marketed eight-lamp photoflash unit employing radiationswitches is described in U.S. Pat. Nos. 3,894,226 and 4,017,728 andreferred to as a flip flash. A ten-lamp version is described in U.S.Pat. Nos. 4,156,269 and 4,164,007. The unit comprises a planar array ofhigh voltage flashlamps mounted on a printed circuit board with an arrayof respectively associated reflectors. Circuitry on the board includes aplurality of solid state switches that chemically change from a high tolow resistance, so as to become electrically conducting after exposureto the radiant heat energy from an ignited flashlamp operativelyassociated therewith. The lamps of the array are arranged in two equalgroups disposed in the upper and lower halves respectively of therectangular-shaped circuit board. A pair of terminal contacts at thelower end of the unit is provided for activation of the upper group oflamps while a set of terminal contacts at the top of the unit isoperatively associated with the lower group of lamps. The application ofsuccessive high-voltage pulses (e.g., 500 to 4,000 volts from, say, apiezoelectric source controlled by the shutter of a camera in which thearray is inserted) to the terminal contacts at the lower end of the unitcauses the lamps at the upper half of the array to be sequentiallyignited. The array is then turned end for end and again inserted intothe camera in order to flash the remaining group of lamps. In the flipflash unit, therefore, all of the lamp sequencing circuitry isself-contained in the removable photoflash unit, and the only functionof the camera is to produce successive firing pulses in response toactuation of the camera shutter.

Another type of multilamp photoflash array currently on the marketemploys lamp-reflector units in linear rows facing in oppositedirections, such as described in U.S. Pat. Nos. 3,598,984; 3,598,985;and 4,032,769 and referred to as a flash bar. Typically, such linearphotoflash lamp arrays comprise a total of ten lamps arranged in twoparallel rows of five lamps each, the lamps and reflectors of one rowbeing staggered relative to the lamps and reflectors of the other row.The five lamps facing in one direction are connected to a respectivefiring circuit disposed on one side of a printed circuit board having aplug-in tab, and the five lamps facing in the opposite direction areconnected to a respective firing circuit on the opposite side of theprinted circuit board. Each of the lamps has a pair of lead-in wires,one of which is connected to a common circuit run which leads to acommon terminal on the plug-in tab, while the other lead-in wire of eachof the lamps of a group of five facing in one direction are connected torespective conductor runs leading to a set of five selective terminalson the respective side of the circuit board tab, e.g., see theaforementioned U.S. Pat. No. 3,598,985. The circuitry of this prior artflash bar unit contains no switching elements; hence, as described, forexample, in U.S. Pat. Nos. 3,618,492 and 3,757,643, one-at-a-timesequencing of the five lamps facing in one direction is provided bysequential application of low voltage firing pulses across theassociated common terminal and successive ones of the associatedselective terminals. That is, when the linear flash bar array is pluggedinto a camera, each time the shutter is actuated, electronic switchingcircuitry in the camera successively applies firing pulses in sequenceto the five selective terminals (and associated common terminal) on theside of the circuit board to which the five lamps facing the camerasubject are connected. When the five lamps facing in one direction areexpended, the flash unit must be removed from the camera, rotated 180degrees, and then reinserted in the camera circuit so that the fiveunused lamps are connected to the camera switching circuitry.

In the interests of compactness, simplicity of operation, and increasingthe number of flash illuminated photographs that may be taken in rapidsuccession, it is desirable to provide a multilamp photoflash array inwhich all of the lamps face in the same direction and only a single setof connector terminals is required, so that removal and reorientation ofthe flash unit is unnecessary. Further, it is particularly desirable toprovide a photoflash lamp array which is compatible with existing cameracircuitry.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aphotoflash lamp array having improved circuit means for permittingreliable flashing of all of the lamps of the array in a predeterminedsequence in response to firing pulses applied to a single set ofterminal means.

A principal object of the invention is to provide an improved switchingcircuit for an array of photoflash lamps which is adapted for operationby a firing pulse switching circuit capable of sequencing only one halfof the total number of lamps of the array but including a monitoringfunction for pretesting unexpended lamps.

These and other objects, advantages and features are attained, inaccordance with the invention, by a photoflash lamp array having circuitmeans for sequentially flashing pairs of lamps (one lamp at a time) inthe array using only one selective terminal per lamp pair together witha common circuit terminal. The array comprises: a plurality of 2nflashlamps, each having a pair of lead-in wires; a common terminal meansconnected to one lead-in wire of each of the 2n lamps; and a pluralityof n selective terminal means, each associated with a respective pair ofthe 2n lamps and directly connected to the non-common lead-in wire ofone of the lamps of the respective pair. The array further includes aplurality of n normally open switches, each of which is coupled betweenthe non-common lead-in wires of an associated one of the respectivepairs of 2n lamps. In operation, the common and selective terminal meansare adapted for connection to a source of firing pulses, and each of theswitches are responsive to the flashing of the directly connected lampof an associated pair so as to connect the other lamp of that associatedpair to the associated selective terminal means. Preferably, each of theswitches comprises a solid state radiation switch located external ofthe lamps and forming part of an electrical circuit between thenon-common lead-in wires of an associated pair of lamps. Each switch iscapable of conversion from a high electrical resistance to a lowelectrical resistance when exposed to radiation emitted from theflashlamp disposed adjacent to the switch, and each of the switches isdisposed adjacent to the lamp of the associated pair which is directlyconnected to a selective terminal means.

The lamps have a filament-type ignition means, and the resistance valueof each lamp filament lies within a predetermined range of resistancevalues. In this manner, the firing circuit to which the lamp arrayterminal means are connected can perform a monitoring function bypassing a current of limited predetermined maximum value through eachunexpended flashlamp to derive alignment signals which function to aligna flashlamp sequencing circuit to bypass inoperative flashlamps.

Accordingly, if the photoflash array comprises ten lamps operated from acommon terminal means and five selective terminal means, a first firingpulse will cause ignition of the directly connected lamp of a first pairof lamps, whereupon the normally open radiation switch associated withthat pair of lamps will be converted from a high to low resistance so asto directly connect the second of the first pair of lamps to the firstterminal means. Thereafter, the second firing pulse will bypass theexpended first lamp and cause the second lamp to be ignited via theactuated radiation switch associated therewith. The third firing pulsewill then be applied to the second terminal means connected to thesecond pair of lamps to ignite the lamp directly connected to thatsecond terminal means. This firing sequence proceeds through theremaining lamps and lamp pairs as described with respect to the firstlamp pair.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE of the drawing is an electrical schematic circuitdiagram of a preferred embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawing, the photoflash lamp array illustratedschematically is provided with a common terminal 10 and five selectiveterminals 11-15 adapted for engagement with the socket contacts of asource of lamp firing pulses. For example, the terminals 10 and 11-15may comprise conductive terminals on the tab of a printed circuit boardsuch as that described in the aforementioned U.S. Pat. Nos. 3,598,985and 3,757,643, which may be incorporated in a camera or a flashattachment for use with the camera and adapted to generate low voltagepulses in synchronization with the actuation of a camera shuttermechanism.

The photoflash array includes a plurality of photoflash lamps 21-30,which may be of a conventional type, such as Sylvania type AG-1, eachcontaining a filament 16 connected across a pair of lead-in wires 21a,21b, etc., and adapted for initiating a flash of combustible materialcontained within the bulb. One lead-in wire, 21b-30b, of each of theflashlamps is connected to the common terminal 10.

In accordance with the invention, the array of ten lamps 21-30 arearranged in five pairs which are respectively associated with the fiveselective terminals 11-15. Each of the selective terminals 11-15 isdirectly connected in electrical circuit to the non-common lead-in wireof one of the lamps of a respective pair of lamps. That is, terminal 11is directly connected to lead-in wire 21a of lamp 21; selective terminal12 is directly connected to lead-in wire 23a of lamp 23; terminal 13 isdirectly connected to lead-in wire 25a of lamp 25; terminal 14 isdirectly connected to lead-in wire 27a of lamp 27; and the selectiveterminal 15 is directly connected to lead-in wire 29a of lamp 29.

The array circuit further includes a plurality of flash-actuated,normally open switches 31-35 which are positioned external of andadjacent to respective ones of the lamps of the array which are directlyconnected to the selective terminals. Further, each of these switches iscoupled in electrical circuit between the non-common lead-in wires of arespective pair of lamps. More specifically, a first switch 31 iscoupled between lead-in wires 21a and 22a and disposed adjacent to thefirst lamp 21, as indicated by the dashed line arrow 41; a second switch32 is coupled between lead-in wires 23a and 24a and associated with orpositioned near the third lamp 23 as indicated by the dashed line arrow42; a third switch 33 is coupled between lead-in wires 25a and 26a anddisposed adjacent to the fifth lamp 25 as indicated by the dashed linearrow 43; a fourth switch 34 is coupled between lead-in wires 27a and28a and disposed adjacent to the seventh lamp 27, as indicated by thedashed line arrow 44; and a fifth switch 35 is coupled across lead-inwires 29a and 30a and positioned adjacent to the ninth lamp as indicatedby the dashed line arrow 45.

The flash-actuated switches 31-35 may comprise radiation-responsiveswitches each having a pair of electrical contacts urged into contactwith each other but held apart, for example, by a plastic material whichmelts or otherwise deforms when heated by the heat generated when theassociated lamp flashes, so as to permit the contacts to close andelectrically connect the next lamp in the array across a respectiveselective terminal and the common terminal. For example, U.S. Pat. No.4,087,849 describes a multilamp photoflash unit havingradiant-energy-activated quick-connect switches each comprising a pathof heat shrinkable polymeric material attached to a circuit board andextending across an aperture therein to restrain a resilient movablecontact in a spaced relation to a fixed circuit contact.

Alternatively, the radiation-responsive material may be a chemical orcomposition bridged between or encapsulating a pair of spaced-apartterminals and which is normally an insulator and becomes electricallyconductive when heated by an associated flashing lamp, thereby formingan electrical connection to the next lamp to be flashed in the circuit.More specifically, consider a preferred application wherein thedescribed photoflash array circuitry comprises conductor runs disposedin a pattern on a printed circuit board. In this case, theradiant-energy-activated, normally open connect switches 31-35 are incontact with and bridge across circuit runs that are connected to them.More specifically, each switch preferably comprises a solid state massof material interconnected to a pair of spaced-apart electricalterminals in the circuit. The material for the connect switch isselected to be of the type initially having an open circuit or highresistance, the resistance thereof becoming converted to a lower valuewhen the material receives radiation in the form of heat and/or lightfrom a respective adjacent lamp being flashed. One type of solid stateswitch which operates in this manner is described in U.S. Pat. No.3,458,270 of Ganser et al, in which the use of silver oxide in apolyvinyl binder is taught as a normally open radiant energy switch.Upon radiant heating, the silver oxide decomposes to give a metallicsilver residue which is electrically conductive.

A preferred switch composition for a photoflash array operated by lowvoltage firing pulses is described in a copending application Ser. No.148,358, filed May 9, 1980, assigned to the present assignee, andcomprises a dried weight 35-70% silver carbonate and/or silver oxide,30-60% silver-coated glass beads, and 1-20% binder. Furthermodifications of the switch composition for facilitating control of theswitch conversion time are described in a copending application Ser. No.148,119, filed May 9, 1980, assigned to the present assignee.

The circuit functions as follows upon the terminals 10 and 11-15 beingconnected to a source of firing pulses, for example, such as describedin the previously mentioned U.S. Pat. Nos. 3,618,492 and 3,757,643.Assuming that none of the ten lamps of the unit have been flashed, uponoccurrence of a first firing pulse across terminals 10 and 11, thispulse will be directly applied to the lead-in wires of the firstconnected flashlamp 21, whereupon the lamp 21 flashes and becomes anopen circuit between its lead-in wires 21a and 21b. Heat and/or lightradiation from the flashing first lamp 21 is operative via path 41 toactivate the normally open switch 31. The radiation causes the normallyopen connect switch 31 to become a closed circuit (or a low value ofresistance), thereby connecting selective terminal 11 to the second lamp22. By the time this occurs, the first firing pulse should havediminished to a value insufficient to cause the second lamp 22 to flash.

In the electronic circuit described in the aforementioned U.S. Pat. No.3,618,492, a monitoring function is provided wherein a current oflimited predetermined maximum value is applied through each unexpendedflashlamp. This monitoring current is generated prior to the ignition ofa given one of the flashlamps. In this manner, alignment signals arederived which function to align the flashlamp sequencing circuit tobypass inoperative flashlamps. This monitoring function is dependentupon the resistance across the lamp lead-in wires. Accordingly, theresistance values of lamp filaments are selected to lie within apredetermined range; typically, the filament in each lamp has aresistance value in the range of about 0.5 to 1.5 ohms. Thus, if themonitoring circuit senses a significantly higher resistance across thelamp lead-in wires, say, for example, higher than 50 ohms or 75 ohms,the selected terminal connected to that lamp will be bypassed, and thefiring pulse will be applied across the operative lamp connected to thenext successive selective terminal. On the other hand, if the monitoringcircuit senses a resistance below the preselected level (that is below50 ohms or 75 ohms) a firing pulse will be applied to the selectiveterminal connected to that lamp.

In the present instance, with the first lamp 21 having been fired, butwith the switch 31 having been closed, the monitoring circuit wouldcontinue to sense an unexpended lamp, namely, lamp 22, connected to theselective terminal 11. Accordingly, when the next firing pulse occurs,it is applied to the lead-in wires of the second lamp 22, via the nowclosed connect switch 31, whereupon the second lamp 22 flashes. Sinceboth lamps 21 and 22 have not been fired, the monitoring circuit willcause the firing pulse alignment to bypass terminal 11 and proceed toterminal 12, to which the unexpended lamp 23 is directly connected.Hence, when the next firing pulse occurs, it is applied directly to thethird lamp 23 thereby firing that lamp, whereupon the radiation fromlamp 23 activates connect switch 32 to become essentially a closedcircuit across its terminals. The next firing pulse will be applied viathe now closed connect switch 32 to the lead-in wires of the fourthflashlamp 24, thereupon causing that lamp to flash. The foregoingpattern of operation then continues with respect to selective terminals13, 14 and 15 to cause the sequential firing of lamps 25-30. Hence, inaccordance with the invention a total of 2n (10) lamps have been ignitedfrom n (5) selective terminals together with a common terminal.

Accordingly, although the invention has been described with respect tospecific embodiments, it will be appreciated that modifications andchanges may be made by those skilled in the art without departing fromthe true spirit and scope of the invention. For example, various typesof flash-actuated switches may be employed as elements 31-35; varioustypes of circuit conductors and terminals may be employed; and n may betwo or greater, i.e., the circuit approach is applicable to arrays offour lamps, six lamps, eight lamps, etc.

We claim:
 1. A photoflash lamp array comprising, in combination:aplurality of 2n flashlamps, each having a pair of lead-in wires; acommon terminal means electrically connected to one lead-in wire of eachof said 2n lamps; a plurality of n selective terminal means, eachassociated with a respective pair of said 2n lamps and directlyconnected in electrical circuit to the non-common lead-in wire of one ofthe lamps of the respective pair; and a plurality of n normally openswitches, each coupled in electrical circuit between the non-commonlead-in wires of an associated one of said respective pairs of 2n lamps;said common and selective terminal means being adapted for connection toa source of firing pulses, and each of said switches being responsive tothe flashing of the directly connected lamp of an associated pair so asto electrically connect the other lamp of said associated pair to theassociated selective terminal means.
 2. The photoflash lamp array ofclaim 1 wherein each of said n switches is a radiation switch capable ofconversion from a high electrical resistance to a low electricalresistance when exposed to radiation emitted from a flashlamp disposedadjacent to the switch, and each of said switches is disposed adjacentto the directly connected lamp of the associated pair of lamps to whichthe switch is electrically coupled.
 3. The photoflash lamp array ofclaim 2 wherein each of said switches is a solid state radiation switchlocated external of the lamps and forming part of an electrical circuitbetween the non-common lead-in wires of an associated pair of saidlamps.
 4. The photoflash lamp array of claim 1 wherein each of saidlamps has a filament connected across the lead-in wires thereof.
 5. Thephotoflash lamp array of claim 4 wherein the resistance value of saidlamp filament lies within a predetermined range of resistance values. 6.The photoflash lamp array of claim 4 wherein said filament of each ofsaid lamps has a resistance value in the range of about 0.5 to 1.5 ohms.7. The photoflash lamp array of claim 6 wherein each of said switches isa solid state radiation switch located external of the lamps and formingpart of an electrical circuit between the non-common lead-in wires of anassociated pair of said lamps.
 8. The photoflash lamp array of claim 7wherein n=5.